This application is based on and claims priority to Japanese Patent Application No. 2001-184926, filed Jun. 19, 2001, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
This invention relates generally to a cooling arrangement for an outboard motor, and more particularly to an improved cooling arrangement for delivering coolant to multiple locations of an outboard motor.
2. Description of Related Art
An outboard motor typically includes a housing unit that can be mounted on an associated watercraft and an internal combustion engine disposed above the housing unit. The housing unit carries a propulsion device such as, for example, a propeller to propel the watercraft. The engine powers the propulsion device with a driveshaft and a propulsion shaft extending through the housing unit.
Typically, an exhaust system is provided to route the exhaust gases from the engine to a location out of the outboard motor through the housing unit. The engine and the exhaust system build heat because air/fuel charges burn in combustion chamber(s) and then the burnt charges, i.e., exhaust gases, pass through the exhaust system. Typically, the outboard motor has a cooling water delivery system to deliver water taken from a body of water surrounding the outboard motor to the engine and the exhaust system for cooling purposes.
The cooling water delivery system can be arranged adjacent to the exhaust system upstream of the engine. Because an exhaust manifold and an exhaust passage connected to the manifold normally are disposed offset on one side of the outboard motor, a water passage or jacket inevitably is disposed on the same side. Accordingly, another side of the outboard motor tends to become hot and occasionally is damaged thereby. For example, an outer surface of the housing unit on the side spaced apart from the water passage can become discolored.
In addition, an outboard motor employing a four-cycle engine typically includes a lubricant reservoir disposed below the engine within the housing unit. The lubricant reservoir accumulates lubricant oil that has circulated in the engine for lubrication of engine portions. The lubricant reservoir thus can build heat therein also. Because the lubricant in the reservoir is recycled, the heat should be removed before the oil is recirculated through the engine. In some arrangements, the heat of the lubricant reservoir can also expedite the discoloring phenomenon noted above.
A need therefore exists for an improved cooling arrangement for an outboard motor that can sufficiently cool both sides thereof even if a coolant delivery system is disposed offset on one side.
In accordance with one aspect of the present invention, an outboard motor comprises a housing unit adapted to be mounted on an associated watercraft. An internal combustion engine defines a first exhaust passage and a first lubricant passage. The first exhaust passage generally extends on a first side of the outboard motor. The first lubricant passage generally extends on a second side of the outboard motor opposite to the first side. A support member is coupled with the housing unit to support the engine above the housing unit. An exhaust conduit depends from the support member within the housing unit. The support member defines a second exhaust passage connecting the exhaust conduit with the first exhaust passage. The second exhaust passage generally extends on the first side. A lubricant reservoir depends from the support member within the housing unit. The support member defines a second lubricant passage connecting the lubricant reservoir with the first lubricant passage. The second lubricant passage generally extends on the second side. The engine and the support member together define a first coolant passage extending in the vicinity of the first and second exhaust passages. Either the engine or the support member defines a second coolant passage extending from the first coolant passage toward a location in the vicinity of either the first or second lubricant passage.
In accordance with another aspect of the present invention, an outboard motor comprises a bracket assembly adapted to be mounted on an associated watercraft. A drive unit is supported by the bracket assembly for tilt movement about a generally horizontally extending tilt axis and for steering movement about a generally vertically extending steering axis. The drive unit comprises an internal combustion engine disposed atop thereof. An exhaust system is arranged to discharge exhaust gases from the engine. The exhaust system at least in part is generally disposed on a first side of the drive unit. A coolant delivery system is arranged to cool either the engine or the exhaust system. The coolant delivery system at least in part is generally disposed on the first side of the drive unit. The coolant delivery system includes a coolant passage extending toward a second side of the drive unit opposite to the first side. The coolant passage extends generally horizontally and parallel to the tilt axis.
In accordance with a further aspect of the present invention, an outboard motor comprises a bracket assembly adapted to be mounted on an associated watercraft. A drive unit is supported by the bracket assembly. The drive unit comprises an internal combustion engine disposed atop thereof The engine includes at least one cylinder having a generally horizontally extending axis. An exhaust system is arranged to discharge exhaust gases from the engine. The exhaust system at least in part is generally disposed on a first side of the drive unit. A coolant delivery system is arranged to cool either the engine or the exhaust system. The coolant delivery system at least in part is generally disposed on the first side of the drive unit. The coolant delivery system includes a coolant passage extending to a second side of the drive unit opposite to the first side. The coolant passage extends generally horizontally and normal to the axis of the cylinder.